1. Field of the Invention
The present invention relates to a color-bar signal generation unit compatible with a plurality of television signal formats. More particularly, this invention is concerned with a color-bar signal generation unit for generating a color-bar signal that enables broadcasting conforming to both the high-definition television (HD) format and the standard-definition television (SD) format including the National Television System Committee-recommended (NTSC) format. Using the color-bar signal produced by the novel color-bar generation unit in accordance with the present invention, both a 16:9 aspect ratio picture produced in the HD format and a 4:3 aspect ratio picture resulting from conversion of the HD picture into the SD format can be broadcast according to the same procedure as that adopted when a conventional color-bar signal is used.
2. Description of the Related Art
Digital broadcasting falls into HD broadcasting and SD broadcasting which deliver pictures of different sizes or aspect ratios of 16:9 and 4:3, respectively. Moreover, ongoing broadcasting conforming to the NTSC format may be used. It is therefore becoming a matter of common practice that programs are produced in the HD form, which offers high image quality and which permits the aspect ratio of 16:9, are converted into the SD (including the NTSC) format, and are then broadcast. A color-bar signal is an important signal providing a reference for optimizing pictures. Even when a video signal format is converted into one conforming to the SD format, the color-bar signal should preferably not be replaced with another in order to preserve the original picture.
Preferably, one color-bar signal enables both HD broadcasting and SD broadcasting (including broadcasting conforming to the NTSC format). Using the color-bar signal, both the 16:9 aspect ratio HD picture and the 4:3 aspect ratio picture resulting from conversion of the HD picture into the SD format can be broadcast according to the same procedure as that adopted when a conventional color-bar signal is used.
At present, a 100%-full-color-bar signal is employed in HD broadcasting, and a 100%- or 75%-full-color-bar signal or an SMPTE color-bar signal (a color-bar signal recommended by the Society of Motion Picture and Television Engineers (SMPTE)) is employed in SD broadcasting.
According to the present invention, what is referred to as a 100%-full-color-bar signal (or simply, a color-bar signal) is a color-bar signal that contains red, green and blue color signals whose levels corresponds to 100% of their designed level. Moreover, this color-bar signal represents a color-bar test pattern composed of color bars that include red, green, and blue bars, and combinations thereof and that are arranged over a whole screen in descending order of the level of a relevant luminance signal from the left side of the screen. What is referred to as a 75%-full-color-bar signal is a color-bar signal containing red, green, and blue color signals whose levels correspond to 75% of their designed level. This color-bar signal also represents a color-bar test pattern composed of color bars that include red, green, and blue bars, and combinations thereof and that are arranged over a whole screen in descending order of the level of a relevant luminance signal from the left side of the screen. These color-bar signals are structured in conformity with the different video signal formats. The color-bar signal structured in conformity with the HD format (16:9) is not intended to be used even after the video signal format is converted into one conforming to the SD format (4:3) (this conversion shall be referred to as down-conversion). The SMPTE color-bar signal contains a chroma control signal for use in controlling saturation on a monitor. Nevertheless, the SMPTE color-bar signal is employed in NTSC broadcasting.
The chroma control signal for use in controlling saturation on an SMPTE monitor cannot be used to control saturation on an HD monitor that handles a luminance signal and chrominance signals as signal components.
Along with down-conversion of the video signal format representing a program, a color-bar signal conforming to the HD format (16:9) must be down-converted into one conforming to the SD format (4:3), representing a color-bar test pattern displayed on a full screen. At this time, signal components representing portions of the color-bar test pattern that appear on both sides of the screen are cut off. The resultant signal cannot therefore be used as a color-bar signal. The color-bar signal must therefore be replaced with another. However, the replacement impairs the original video signal. For this reason, there is an increasing demand for a color-bar signal usable in common for the HD and SD formats.
For NTSC (SD) broadcasting, the SMPTE color-bar signal (75%-full-color-bar signal) is usually adopted. The HD 100%-full-color-bar signal resulting from down-conversion may be taken for the 75%-full-color-bar signal differs from the HD 100%-full-color-bar signal solely in terms of the signal level. Moreover, when the level of the color-bar signal is adjusted incorrectly and broadcast, a broadcasting error occurs.
A vector scope is used to manage colors of a picture produced in the NTSC form. In particular, a color of a face (flesh color) reflects the condition of health. Viewers are conscious of the face color. Therefore, a video signal is magnified with the amplitude of a color burst used as a reference in order to monitor the face color (FIG. 9C). However, an HD video signal containing a luminance signal and chrominance signals as components does not have a component corresponding to the color burst contained in the NTSC video signal.
Signals whose levels correspond to xc2x12% of the designed level are adopted as luminance control signals used to control luminance on a monitor and are contained in an HD color-bar signal. Signals whose levels correspond to xc2x14% thereof are adopted as the luminance control signals contained in an SD color-bar signal. However, a down-converter does not output signal components of negative levels (numeral 63 in FIG. 6 or numeral 71 in FIG. 7). Therefore, the signal whose level corresponds to xe2x88x924% thereof cannot be adopted as one of the luminance control signals contained in the SD color-bar signal (numerals 111 and 112 in FIG. 11).
The SMPTE color-bar signal employed in NTSC broadcasting cannot be used to control saturation on an HD monitor that handles a luminance signal and chrominance signals as signal components (FIG. 10A).
An object of the present invention is to provide a color-bar signal generation unit compatible with a plurality of television signal formats.
In detail, an object of the present invention is to provide a color-bar signal generation unit for generating a color-bar signal enabling both HD broadcasting and SD broadcasting (including NTSC broadcasting). Using the color-bar signal produced by the novel color-bar signal generation unit in accordance with the present invention, both a 16:9 aspect ratio HD picture of and a 4:3 aspect ratio picture resulting from conversion of the HD picture into the SD format can be broadcast according to the same procedure adopted when a conventional color-bar signal is used.
The first point to which the present inventors have directed their attention in efforts to accomplish the foregoing object will be described below. In general, the problems underlying the related art are presumably solved by producing a color-bar signal composed of an HD color-bar signal and an SD color-bar signal. The HD color-bar signal is assign to a 16:9 aspect ratio color-bar test pattern for HD broadcasting, while the SD color-bar signal is assigned to a 4:3 aspect ratio color-bar test pattern for SD broadcasting. However, the waveform of the color-bar signal displayed on a waveform monitor becomes more complex than that of a conventional one. A conventional method of observing the waveform using the waveform monitor must therefore be modified.
According to the present invention, the 4:3 aspect ratio SD portion of the 16:9 aspect ratio HD color-bar test pattern is represented by a 100% white signal and a 75% color-bar signal that serve as an NTSC color-bar signal. Portions outside the SD portion are represented by part of a 100% color-bar signal serving as the HD color-bar signal (FIG. 2). This is attributable to the fact that the portions of the HD color-bar test pattern outside the SD portion are used merely as part of the HD color-bar test pattern.
Reasons why part of the 100% color-bar signal serves as the HD color-bar signal will be described below.
When a color-bar signal is used to adjust or check the level of a video signal produced by a television system, the levels of red, green, and blue signals contained in the video signal can be adjusted using a 100% white signal. For adjusting the levels of a luminance signal Y and chrominance signals Pb and Pr, reference signals are needed.
(1) The level of the luminance signal Y is adjusted using the 100% white signal contained in the SD color-bar signal.
(2) For adjusting the chrominance signal Pb contained in the video signal, the level of the chrominance signal Pb relevant to a yellow signal(Ye) contained in the color-bar signal is brought to xe2x88x9250% of the designed level. The level of the chrominance signal Pb relevant to a blue signal(B) contained therein is brought to +50% thereof. Both or either of a 100% yellow signal and a 100% blue signal is therefore needed.
(3) For adjusting the chrominance signal Pr contained in the video signal, the level of the chrominance signal Pr relevant to a cyan signal(CY) contained in the color-bar signal is brought to xe2x88x9250% of the designed level. The level of the chrominance signal Pr relevant to a red (R) signal contained therein is brought to +50% thereof. Both or either of a 100% cyan signal and a 100% red signal is therefore needed.
The HD color-bar signal is used to adjust the level of a video signal in consideration of the points described below.
(1) For adjusting the chrominance signal Pb contained in the video signal, the levels of chrominance signals Pb relevant to the yellow and blue signals contained in the color-bar signal are brought to 100% of their designed level. For adjusting the chrominance signal Pr contained therein, the levels of the chrominance signals relevant to the cyan and red signals contained therein are brought to 100% thereof.
(2) The chrominance signal Pb exhibits a waveform protruding rightward.
Consequently, the chrominance signal Pb relevant to the blue signal contained in a color-bar signal is used to adjust the chrominance signal Pb contained in a video signal. The chrominance signal Pr relevant to the cyan signal contained therein is used to adjust the chrominance signal Pr contained therein. A blue bar is displayed on the right end of a screen, and a cyan bar is displayed on the left end thereof. The blue signal and cyan signal representing the blue and cyan bars are signals whose levels correspond to 100% of their peak value (numerals 24 and 25 in FIG. 2, and numerals 43 and 44 in FIG. 4).
The second point to which the present inventors have directed their attention in efforts to accomplish the aforesaid object will be described below. The SD (4:3) portion of the HD (16:9) color-bar test pattern is represented by a 100% white signal and a 75% color-bar signal that serve as an NTSC color-bar signal (numerals 21 and 30 in FIG. 2). The reasons why the white signal and color-bar signal are adopted will be described below.
(1) The 100% white signal can be shared by the HD color-bar signal representing the HD color-bar test pattern and the SD color-bar signal representing the SD portion, and can be used to control white balance on a monitor.
(2) An SMPTE color-bar test pattern represented by a 75% color-bar signal is usually employed in NTSC broadcasting.
(3 ) A 100% color-bar signal may be clipped by an NTSC television system when the signal level rises to a level corresponding to about 110%. (The positive peak level of the 100% color-bar signal employed in NTSC broadcasting may reach 133%.)
(4) A scale appearing on an NTSC waveform monitor indicates a maximum level of 120% at a positive side.
(5) Color bars represented with a 100% color-bar signal employed in HD broadcasting are arranged outside the 4:3 portion of the test pattern (numerals 24 and 25 in FIG. 2).
The third point to which the present inventors have directed their attention in efforts to accomplish the aforesaid object will be described below. Namely, a video signal is magnified so that the amplitude of a color burst will be indicated on a circular scale presented by a vector scope. This is intended to facilitate observation of a flesh color in an NTSC picture. A signal representing the flesh color is indicated near an +I axis presented by an NTSC vector scope (FIG. 9C). According to the present invention, a flesh color reference signal meeting the conditions described below is newly added to a color-bar signal (numeral 26 in FIG. 2, numeral 41 in FIG. 4A, numeral 42 in FIG. 4B, and numeral 61 in FIG. 6).
(1) The signal should be indicated to have the same amplitude as the color burst on the +I axis presented by the NTSC vector scope.
(2) The waveform of the signal displayed on the NTSC waveform monitor should not interfere with observation of the waveforms of components of a color-bar signal.
Consequently, when an HD vector scope is used, a video signal is magnified in the same manner as an NTSC video signal, and the foregoing flesh color reference signal (+I signal) is employed. Thus, the flesh color can be monitored in the same manner as that in the NTSC picture (FIG. 8). (In this point, the HD vector scope is analogous to the NTSC vector scope.)
The fourth point to which the present inventors have directed their attention in efforts to accomplish the aforesaid object will be described below. A luminance control signal for use in controlling luminance on a monitor is standardized for each of the HD and SD formats (a xc2x12% signal is adopted according to the HD format, and a xc2x14% signal is adopted according to the SD format). However, when a color-bar signal is down-converted into the SD format, signal components of negative levels are not output. According to the present invention, a +2% signal is substituted for a xe2x88x924% signal contained in an SD color-bar signal (numeral 28 in FIG. 2, numeral 51 in FIG. 5A, and numeral 62 in FIG. 6). For controlling luminance on a monitor, a color bar represented by the +4% signal is made visible on the monitor but a color bar represented with the +2% signal is made invisible (numerals 113 and 114 in FIG. 11). The luminance is controlled to fall within the range of luminance values attained in the monitor using the xc2x14% signals.
The fifth point to which the present inventors have directed their attention in efforts to accomplish the aforesaid object will be described below. Assuming that color bars represented with a red signal and its relevant signals alone contained in an SMPT color-bar signal are displayed on a monitor in order to adjust the chrominance signal Pr contained in a video signal, a color bar represented with a reference signal serving as a reference for comparison disappears from a monitor. This makes it impossible to relatively equalize the brightness of a color bar and that of the reference color bar while viewing the monitor. Consequently, the chrominance signal Pr contained in the video signal cannot be adjusted (numerals 101 and 102 in FIG. 10).
According to the present invention, a reference white signal of level 75% is used as a chroma control reference signal for use in controlling saturation on a monitor. The color bar represented by the 75% reference white signal is displayed adjacently to other color bars, which are represented by a 75% color-bar signal, on the monitor. When the chrominance signal Pr contained in a video signal is adjusted, a red signal contained in the 75% color-bar signal is varied. However, the 75% reference white signal representing the white bar adjacent to the red bar will not be varied. In principle, the red and white signals have a level corresponding to 75% relative to their designed level. For adjusting the chrominance signal Pr, therefore, only the color bars represented by the red signal and its relevant signals contained in the color-bar signal are displayed on the monitor. Then, the brightness of the red bar and that of the white bar (numerals 103 and 104 in FIG. 10) are relatively equalized.
According to the present invention, there is provided a color-bar signal generation unit including first, second, and third color-bar signal generators for generating a color-bar signal that represents a 16:9 aspect ratio color-bar test pattern, and a color-bar signal switch for switching outputs of the generators. Herein, the color-bar signal representing the 16:9 aspect ratio color-bar test pattern contains a 75% color-bar signal and 100% color-bar signals. The 75% color-bar signal represents a portion of the color-bar test pattern defined with the aspect ratio of 4:3 and serves as an NTSC color-bar signal. The 100% color-bar signals represent portions thereof outside the portion with the aspect ratio of 4:3 and serve as components of an HD color-bar signal. Thus, the color-bar signal representing a 16:9 aspect ratio color-bar test pattern is used in common for the HD format stipulating the aspect ratio of 16:9 and the NTSC format stipulating the aspect ratio of 4:3.
In the color-bar signal generation unit, a flesh color signal may be acquired in order to enable monitoring of the hue of the flesh color using a vector scope.
In the color-bar signal generation unit, a white signal having the same level as a signal that represents a color-bar test pattern may be used as a chroma control reference signal. A white bar represented by the signal is displayed adjacent to color bars in order to enable control of saturation on an HD monitor that handles a luminance signal and chrominance signals as signal components or an SD monitor that handles these signals in the form of a composite signal.
In the color-bar signal generation unit, three signals of positive levels including a zero level may be included in order to enable control of luminance on a monitor.
When a color-bar signal generated by the color-bar signal generation unit is employed in broadcasting a 16:9 aspect ratio HD picture, even if the HD picture is down-converted into the SD form (including the NTSC format stipulating the aspect ratio of 4:3), the color-bar signal need not be replaced with another but can be used as it is.